Resolving macroscale and microscale heterogeneity in virus filtration

In this paper, we characterize the filtration and deposition profiles of a recombinant analog of Norwalk virus, an important waterborne pathogen, in p acked beds of saturated quartz sand under both 'clean-bed' and 'dirty-bed' conditions. Under clean-bed conditions with NaCl as the electrolyte, the re tained Norwalk virus particles decline like a power-law with depth. The pow er-law decay in retained particle concentration is consistent with the pred ictions of a recently proposed filtration model which assumes that microsca le heterogeneity leads to particle filtration length scales of all sizes; i .e. the filtration is fractal in nature. However, under dirty-bed condition s with either ground water or wastewater as the pore fluid, the deposited N orwalk virus particles profiles are considerably more complex. Analysis of these data using both the traditional filtration model and the fractal filt ration model suggests that, under dirty-bed conditions, macroscale heteroge neity dominates virus removal rates. (C) 2001 Elsevier Science B.V. All rig hts reserved.